High Folks, Its been a long time since I did the cello due to a mixture of dreadfull weather, work and family commitments but the journey continues.
The back plate was glued up using fresh hide glue. It took about 2 hrs to accurately plane the edges square and get a good contact along the entire length of the joint.
This joint is of absolute importance that it is done right, surface contact, glue consistency, etc. Normally on smaller instruments it is sufficient to rub the joint together and let it set but since the cello back is so long I used some clamps to keep it secure while the glue was setting.
Once it was set the flat side was planed level as it is used as a reference surface. You will see in the next blog entry. Its also the surface that goes against the ribs (sides of the cello) and it has to be flat. See how it goes in the photo, also shown is the neck. Thats what we are going to look at now.
Unfortunately I forgot to take pics of the marking out stage so I have substituted a couple of violin pics. The marking out is the same and the peg box is cut in the same way. I usually drill out some of the waste first before chiselling. The peg holes are drilled first while the wood is still in its square form.
Back to the cello scroll. The following pic shows the peg box cut out. Note the taper, its narrower at the bottom. This helps to make stronger walls and a bigger surface contact on the peg to increase friction which stops the pegs slipping.The outside cheeks of the peg box were cut away after the peg box was excavated.
The next job to do is to cut out the scroll. The volute is scribed on by pricking through the drawing shown below.
The cutting is done in three stages, first turn, second turn and eye turn.
The first turn is cut in tangential cuts to the volute line down to the depth of the back of the scroll. Next the waste is chiselled out. This can be tricky as the grain can tear out so you have to be careful about chisel angles and direction of cut. Best to do it slowly and little by little.
The biggest challenge is to get both sides the same so the initial marking out has to be good but also there needs to be constant checking once the first turn is established on each side. The following pic illustrates this quite nicely and the next shows how any discrepency is overcome.
Once both sides have the first turn cut true to the pattern.
Its time to mark out the second turn. Reference to scale drawings are required and sizes transfered using dividers.
The height around the second turn is marked on and the same process of cutting is carried out. I also use a gouge to help true up the curves of the volute. The radius of the gouge needs to be slightly bigger than the volute curve to avoid under cutting.
Next is marking out the eye turn.
I use a junior hacksaw for cutting the eye turn as the blade is less likely to tear the fragile wood at the edges of the eye.
Finally both sides are rough cut and trued up.
The next job is to lighten up the chunky appearance by undercutting the volute using gouges of various sizes and leveling the surfaces to their finished size. Note the bevel on the edges of the eye and the volute of the scroll. This has to be considered all the time when cutting the turns. Removing too much material early on will leave the scroll looking weak and feeble once the bevel is cut at the end of the process.
There is still quite a bit of surface prep work still to do on the scroll, peg box and neck. more will be revealed but at the moment its back to the back plate. A job I have been putting off as it is realy hard work. I made another curved sole plane to do the carving of the back contours. Here it is in its basic form. Check out the design on the side.
Needs finishing but it does work. Amazing what can be done with a 4 inch nail and bit of wood!!
Bye for now
-- Dave D